Archive for the Math & Physics Category

According to calculations, most of the way to the very edge of the universe could be traveled in a human lifetime.

All you need is a rocket capable of accelerating at 9 metres per second per second. You would be traveling at speeds close to the speed of light, so time would be slower for you due to relativity.

Because the universe is expanding, and because that expansion is accelerating, the expansion horizon could never be reached, but you could get 99 percent of the way in 50 years.

Or, as it turns out, in even less time:

[Juliana Kwan at the University of Sydney in New South Wales, Australia] and her colleagues have found the trip could take even less time.

Based on the latest cosmological values for dark energy and other parameters, they showed an astronaut could make the journey in only 30 years.

But their calculations also suggest that returning home presents its own challenges. Even slight uncertainties in the strength of dark energy or the total density of matter in the universe could cause a spacecraft to miss Earth by millions of light years.

Beginning the deceleration just a second too late could cause you to overshoot the Milky Way, Kwan says. “You would effectively be lost in space.” [New Scientist]

Not that it matters. Even if you made it back, 70 billion years would have passed on Earth and nothing you remember would remain- even the Sun would be gone.

Researchers from the Jet Propulsion Laboratory in Pasadena, Calif, have made a mouse levitate – in the name of science, of course!

Scientists working on behalf of NASA built a device to simulate variable levels of gravity. It consists of a superconducting magnet that generates a field powerful enough to levitate the water inside living animals.

[…]

Repeated levitation tests showed the mice, even when not sedated, could quickly acclimate to levitation inside the cage. After three or four hours, the mice acted normally, including eating and drinking.

The strong magnetic fields did not seem to have any negative impacts on the mice in the short term, and past studies have shown that rats did not suffer from adverse effects after 10 weeks of strong, non-levitating magnetic fields. [LiveScience]

If key species in an ecosysyem goes extict the whole system can collapse. Ecologists have created a model for predicting such a collapse by ranking how important a species is using Googles search algorithim PageRank.

This is a new network-based approach to species extinction modelling and could be very useful for conservationists trying to prevent an eco-disaster.

“If we can find the way of removing species so that the destruction of the ecosystem is the fastest, it means we’re ranking species by their importance,” said ecologist Stefano Allesina of the University of California, Santa Barbara, who co-authored the paper published Friday in PLoS Computational Biology.

[…]

“When the researchers tested the Google algorithm against existing models for predicting ecosystem collapse, they found that the new solution outperformed the old ones in each of the 12 food webs they looked at.

“In every case that we tested, the algorithm returned either the best possible solution, out of the billions of possibilities, or very close to it,” Allesina said. In this case, the “best possible solution” is the one that predicts total ecosystem collapse using the fewest number of species extinctions. [Wired]

With PageRank, a website is important if important websites link to it. The researchers applied this idea to ecosystems: if lots of species eat you, you’re important. If lots of important species eat you, you’re even more important.

I’m sure that is a great comfort to the gazelle currently serving as dinner to a bunch of lions somewhere on the African savannah.

Gamma-ray bursts are very powerful and very bright events. They release in a momentary flash of gamma-rays and X-rays more energy than the sun does in its entire lifetime.

(Luckily, their are no sources of these bursts in our galaxy, otherwise we would be toast).

Gamma-ray bursts have been thought to occur because of massive dying stars collapsing into a black hole and bursting with radiation in the process. However, the bursts also have an afterglow of X-ray radiation that this theory can’t explain.

A new theory can. According to the new theory, a gamma-ray burst is the result of a black hole burrowing into a star and eating it from the inside like a gigantic light-devouring parasite.

It remains to be seen if the new theory can also account for other aspects of gamma-ray bursts. Did anyone say paradigm shift?